Prepared by Dr. Eng. Karolina Orłowska
CASE STUDY
Real-time quality control of alkyd resins: correlation of viscosity and acid number with Raman spectra
In alkyd resin production, every minute counts – the faster you detect quality deviations, the fewer costly corrections and material losses. At Gekko Photonics, we demonstrated that Raman spectroscopy combined with advanced chemometrics enables determination of viscosity and acid number in near real-time.
Introduction and Project Context
For alkyd resins in solvents, key quality parameters – viscosity and acid number – are most often verified using laboratory methods on samples taken after filtration. This approach ensures precision but introduces a significant delay between production and quality decision-making.
The project aimed to verify whether the Spectrally platform based on Raman spectroscopy could take on the role of a fast and repeatable „quality sensor,” delivering results in a short time and forming the basis for quality control automation and ultimately process stabilization.
Business Challenge
- Lack of real-time product quality information – laboratory results are available with a delay.
- Risk of detecting deviations only after batch production is completed, which can generate losses and delay product release.
- The complex matrix of resin and solvents causes signal overlap in the spectrum, making simple assignment of a single band to one parameter difficult.
- Flammable solvents are present in the process environment, so future implementation must consider requirements for explosion-hazardous zones.
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Project Objectives
- Assess the feasibility of measuring viscosity and acid number based on Raman spectra for alkyd resins in solvents.
- Build a preliminary chemometric model for predicting quality parameters.
- Define the target implementation concept, with a preferred in-line measurement after filtration, directly in the pipeline.
- Establish the direction for further model validation for predicting intermediate values.
Applied Solution and Project Approach
We conducted feasibility measurements in an at-line configuration using the Spectrally platform, recording Raman spectra for samples with varied matrices and performing replicates to confirm repeatability. We optimized acquisition to integration times below 1 s and averaged spectra multi-scan to improve the signal-to-noise ratio.
Due to spectrum complexity, we applied a whole-spectrum analysis approach and tested two types of predictive models: linear regression and a neural network-based model. Ultimately, we recommend in-line measurement with probe installation after the filtration unit, which provides continuous reading, fast process response, and readiness for further process automation.
Results and Benefits
- Results demonstrated the high potential of Raman technology combined with chemometrics for monitoring alkyd resin quality parameters.
- A coefficient of determination R² > 0.99 was achieved for both viscosity and acid number.
- The predicted measurement uncertainty range for viscosity was approximately ±0.25 Pa·s, with potential for further improvement after expanding the sample database.
- Quality decisions can be accelerated from hours to seconds or tens of seconds, shifting the operational model from reactive control to proactive process monitoring.
- The recommended next step is to expand the calibration set and validate under near-process conditions.
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Contact
Aleksandra Łukasiewicz
If you are facing a similar challenge in chemical process control, quality stabilization, or real-time reaction monitoring, let's discuss a solution tailored to your technological conditions.
- a.lukasiewicz@gekkophotonics.com
- +48 786 867 071